In recent years, development has been under way of techniques for absorbing a collision force input from the front of a vehicle by means of the vehicle body at the time of so-called frontal collision where the collision force acts on the front surface of the vehicle. For example, as a collision force from the front surface is input to the front ends of left and right front side frames, the left and right front side frames buckle to absorb the collision force. It is preferable that progress of the buckling of the left and right front side frames be not hampered by a sub frame. From Patent Literature 1, a different type of technique is known which causes a sub frame to be detached from the left and right front side frames in response to input of a collision force.
In a front section of the vehicle body disclosed in Patent Literature 1, the left and right front side frames are disposed forwardly of, or in front of, a lower dashboard panel partitioning the vehicle body in a front-rear direction. An engine is mounted between the left and right front side frames, and the sub frame for mounting a steering apparatus is disposed immediately rearwardly of, or behind, the engine. The sub frame has a rear end portion superposed from below the lower surfaces of rear end portions of the left and right front side frames and vertically tightened by means of bolts and nuts. The nuts can be detached from the left and right front side frames when a predetermined load has acted thereon. Namely, the rear end portion of the sub frame is mounted to the rear end portions of the left and right front side frames in such a manner that it can be detached in response to the predetermined load having acted thereon.
When a frontal collision of the vehicle has occurred, a collision force from the front causes the left and right front side frames to buckle toward the rear of the vehicle body. As the buckling of the left and right front side frames progresses, the collision force from the front transmits from the left and right front side frames to the engine. Then, the engine moves toward the rear of the vehicle body to collide against the subframe. As a consequence, the sub frame is detached from the left and right front side frames, so that the engine can move further toward the rear of the vehicle body. Thus, the collision force from the front can be absorbed by the buckling of the left and right front side frames further progressing due to the collision force.
In the case of such a sub frame, there is a need to take into consideration a possibility of occurrence of a so-called bending phenomenon where, upon receipt of the collision force, the rear end portion of the subframe bends downward at its halfway region in the front-rear direction before being detached from the left and right front side frames. If such a bending phenomenon occurs, the lower dashboard panel would receive the collision force from the rear end portion of the sub frame when the rear end portion of the sub frame has hit the lower dashboard panel. Because a passenger compartment is located behind the lower dashboard panel, it is preferable that the collision force transmitted from the sub frame to the lower dashboard panel be suppressed as much as possible.